As mold heating devices for heating a tire mold that accommodates a tire, devices described in FIG. 12 and FIG. 13 of a patent document 1 have conventionally been known.
The mold heating device shown in FIG. 12 of the patent document 1 includes a tubular heat shield arranged so as to surround a side surface of a tire mold that accommodates a tire, a tubular ferromagnetic non-conductive member fixed to an inner surface of the tubular heat shield, and induction heating coils fixed to an inner surface of the ferromagnetic non-conductive member. The heat shield is constructed by a non-metal material, a heat shield material, and a nonmagnetic metal material, which are successively laminated from its inner surface side.
The mold heating device described in FIG. 13 of the patent document 1 includes a tubular heat shield arranged so as to surround a side surface of a tire mold, induction heating coils fixed to an outer surface of the tubular heat shield, a tubular ferromagnetic non-conductive member fixed to outer surfaces of the induction heating coils, and a tubular nonmagnetic metal material fixed to an outer surface of the ferromagnetic non-conductive member. The heat shield is constructed by a non-metal material, and a heat shield material, which are successively laminated from its inner surface side.
For the devices shown in FIG. 12 and FIG. 13, it is not necessary to install the induction heating coils on the tire mold, and these devices are thus economical compared with devices, in which the induction heating coils are installed on the tire mold, such as shown in FIGS. 7 and 8 of the patent document 1, for example. Particularly since there are many types of tire molds, factories generally use much more tire molds than mold heating devices. If an induction heating coil is installed for each tire mold, the number of required induction heating coils increases. On the other hand, for the devices shown in FIG. 12 and FIG. 13 of the patent document 1, the number of required induction heating coils is efficiently reduced.
Moreover, in the devices shown in FIG. 12 and FIG. 13, the heat insulation material is arranged so as to cover the circumference of the tire mold, thereby restraining the heat from being emitted from the heated tire mold to the outside, and the energy consumption can thus be reduced.
However, the mold heating devices shown in FIG. 12 and FIG. 13 of the patent document 1 have the following problems during its production. For the device shown in FIG. 12, its assembly needs an operation of installing the induction heating coils on the inner surface of the heat shield, which includes the tubular non-metal material and nonmagnetic metal material, with the ferromagnetic non-conductive member disposed therebetween, and this operation is difficult. For the device, in which the induction heating coils are installed on the outer surface of the tubular heat shield as shown in FIG. 13, the heat shield has to support this induction heating coils, the ferromagnetic non-conductive member that is located outside the induction heating coils, and the nonmagnetic metal material that is located outside the ferromagnetic non-conductive member. Thus, high strength is necessary for the non-metal material that constructs the heat shield. However, it is difficult to manufacture heat shields constructed by a non-metal material, which is tubular-shaped and has high strength, such as a heat shield installed on the tire heating device, and the manufacture thereof accompanies a very high cost.